1. Field of the Invention
The pre sent invention relates to a pointing stick device, and more particularly, to a waterproof pointing device of a keyboard.
2. Description of the Prior Art
A pointing device is usually installed on the keyboard of a notebook computer and provides a means of inputting cursor control signals. It is often installed on the keyboard chassis board with a hole. There are often gaps between the pointing device and the chassis board; therefore, if not careful, liquids, such as water or coffee may accidentally spill on the keyboard and leak into the interior of the keyboard through these gaps. This will adversely affect the functioning of the pointing device and further damage the mainboard installed below the keyboard of the notebook computer.
The structure of a waterproof pointing device according to the prior art is illustrated in FIG. 1 and FIG. 2. FIG. 1 is a sectional diagram of a pointing device 10 according to prior art. FIG. 2 is an exploded diagram of the pointing device 10 shown in FIG. 1. The pointing device 10 is installed on a chassis board 12 with a hole 13. The pointing device comprises a metallic base plate 24 mounted on the bottom side of the chassis board 12 by screws 15, a plastic pedestal 22 mounted between the chassis board 12 and the base plate 24, a clamping unit 28 for clamping the plastic pedestal 22 on the base plate 24, a square control bar 20 vertically fixed on the plastic pedestal 22 and protruding through the hole 13 of the chassis board 12, a rubber cap 14 installed on the top of the control bar 20, and an adapter 16 installed between the rubber cap 14 and the control bar 20. There is also a rubber-like backing 19 adherent to the back of the base plate 24 and a square shaped rubber-like sponge 18 installed exterior to the plastic pedestal 22 on the base plate 24. The rubber-like sponge 18 is clamped between the chassis board 12 and the base plate 24 to prevent leakage of liquid. The pointing device 10 further comprises four sensors 26 individually installed in four directions near the bottom end of the control bar 20 for sensing the movement of the control bar and generating the corresponding sensing signals.
Because the plastic pedestal 22 is fixed with the clamping unit 28 but does not form a waterproof seal, the rubber-like sponge 18 cannot be placed between the chassis and the clamping unit 28. Instead, rubber-like sponge 18 must be placed at the periphery of the plastic pedestal 22. Therefore, it is imperative that the area of the base plate 24 be large enough to accommodate the rubber-like sponge 18. Because the pointing device 10 is installed on the chassis board of the keyboard and the base plate is protruding outward from the chassis board, space must be allowed under the keyboard for both the mainframe as well as the base plate 24. Space for the mainframe is severely limited thus increasing the difficulty of design and assembly. Also, in the above mentioned waterproof pointing device of the prior art, rubber-like sponge 18 can only be used temporarily to prevent liquid from leaking into the keyboard. This is due in part to the fact that the liquid will accumulate in the interior of the rubber-like sponge 18 thus leading to rusting of the metal base plate 24. Eventually, liquid will inevitably leak onto the mainboard and cause damage. The sensor 26 at the bottom of control bar 20 will also be damaged from this liquid.
It is therefore a primary objective of the present invention to provide a waterproof pointing device of a keyboard to solve the above mentioned problem.
In a preferred embodiment, the present invention provides a pointing device of a keyboard which comprises a chassis board for mounting a plurality of keys, the chassis board comprising a hole positioned at its center approximate for mounting the pointing device, the pointing device comprising:
a pedestal installed below the chassis board under the hole of the chassis board;
an elastic pad mounted between the chassis board and the pedestal with a hole positioned below the hole of the chassis board; and
a control bar vertically fixed to the pedestal and protruding through the holes of the elastic pad and the chassis board;
wherein the elastic pad is tightly clamped between the pedestal and the chassis board for preventing liquid above the chassis board from leaking into the space below the chassis board and the pedestal through the hole of the chassis board.
It is an advantage of the present invention that the elastic pad can be tightly clamped between the chassis board and the plastic pedestal for preventing liquid from leaking through the hole of the chassis board into the base plate. Also, no liquid will accumulate on the base plate or the sensors at the bottom end of the control bar and, therefore, the main board below the keyboard will not be subjected to damage by liquid. There are many designs for the elastic pad of the pointing device of the present invention. The elastic pad is installed on top side of the plastic pedestal and only occupies space within the plastic pedestal on the base plate. The base plate may be reduced in size thus further facilitating the installation of the pointing device within a limited space.
This and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.